Presently, in a wafer cleaning process, the wafer is rotated at a high speed and chemical liquids are vertically sprayed to the wafer surface from the spray head of a cleaning apparatus. Since the diameter of the wafer with copper interconnection formed thereon has increases to 300 mm, when the wafer rotates continuously in the cleaning process, the tangential velocity at the center of the wafer is significantly different from that at the edge of the wafer. As a result, when the chemical liquids vertically strike and collide with the wafer surface, different liquid backsplash may occur due to the different tangential velocities at the center and the edge of the wafer. The backsplash of the chemical liquid is larger at the wafer edge where the tangential velocity is higher. Therefore, even the spray head moves at a lower speed, the dissolving photoresist and residues in the grooves at the wafer edge are difficult to be removed. Consequently, there exists a need to solve the problem of the degradation of the cleaning effects caused by the big liquid backsplash occurred when the chemical liquids are sprayed at the edge of wafer surface.